Rapid drainage consolidation method for deep soft soil foundation

Abstract

The invention discloses a rapid drainage consolidation method for a deep soft soil foundation, and relates to the technical field of soft soil foundation treatment.The rapid drainage consolidation method comprises the following steps that S1, a drainage system is designed, specifically, the number and spacing of horizontal drainage layers are determined according to geological survey data and construction period requirements; s2, horizontal drainage system construction, wherein multiple parallel horizontal drainage layers are constructed at the preset depth of the soft soil foundation from bottom to top; s3, construction of a vertical drainage system, wherein vertical drainage bodies are arranged according to the designed interval, and the vertical drainage bodies are made to communicate with all the horizontal drainage layers; s4, deep water collecting and draining well construction; s5, pipeline system integration; and S6, cyclic loading and consolidation are conducted, specifically, pre-pressing loads are applied to the surface of the foundation step by step, after each stage of load is applied or during the maintaining period, gas supercharging equipment is started, underground water in the water collecting and draining well is drained through a gas stripping drainage device, and loading and drainage circulation is formed till the consolidation degree of the foundation reaches the standard. The structure is simple, the construction period can be shortened, and the drainage efficiency and the treatment depth are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of soft soil foundation treatment, in particular to a rapid drainage consolidation method for deep soft soil foundation. BACKGROUND

[0002] Deep soft soil foundation has the characteristics of high water content, low bearing capacity, high compressibility and poor permeability. If the foundation treatment is not proper, it is easy to cause problems such as settlement and instability, which affects the safety of engineering structure. At present, the main methods of foundation reinforcement in engineering include drainage consolidation method, composite foundation method and solidification improvement method, among which the drainage consolidation method is widely used due to its economy and effectiveness.

[0003] However, the traditional drainage consolidation method has significant defects and cannot meet the efficiency and depth requirements of engineering construction: Long construction period: The traditional method needs to rely on external preloading to drive water out, and the construction time usually lasts for 4-6 months or even longer, which seriously restricts the progress of engineering construction; Low drainage efficiency: The horizontal drainage channel is only set on the upper surface of the foundation, and the water needs to be passively squeezed upward against gravity, so the drainage path is long and the resistance is large, resulting in low efficiency; Fast decay of treatment effect: The additional stress gradually decays with the increase of foundation depth, resulting in rapid decline of treatment effect along the depth, and the treatment depth is limited to no more than 20m; Limited depth: The conventional submersible pump drainage has a limit depth, which makes it difficult to achieve effective drainage of deep soft soil, further limiting the treatment depth.

[0004] In summary, the existing drainage consolidation method cannot balance the construction efficiency, treatment depth and reinforcement effect, and it is an urgent need in the field of deep soft soil foundation engineering to develop a rapid, efficient and deep-layer adapted drainage consolidation method. SUMMARY

[0005] The purpose of the present application is to provide a rapid drainage consolidation method for deep soft soil foundation, which can effectively reduce the construction period, improve the drainage efficiency and increase the treatment depth.

[0006] To achieve the above purpose, the present application provides the following solutions: The present application provides a rapid drainage consolidation method for deep soft soil foundation, comprising the following steps: S1, drainage system design: according to the geological survey data and the construction period requirement, the number of layers and the spacing of the horizontal drainage layers to be set are determined; S2, construction of horizontal drainage system: from bottom to top, a plurality of layers of horizontal drainage layers are constructed at the predetermined depth in the soft soil foundation; S3. Construction of vertical drainage system: Vertical drainage bodies are installed on the site at the designed intervals. The vertical drainage bodies intersect and connect with the horizontal drainage layers of each layer. S4. Construction of deep drainage wells: Drainage wells are set up in the site to penetrate into the soft soil foundation, and an air-lift drainage device is installed in the drainage wells. The air-lift drainage device includes an air inlet pipe and a drainage pipe that are interconnected at the bottom. S5. Pipeline system integration: Connect the air inlet pipes of each of the above-mentioned collection and drainage wells to the gas pressurization equipment, connect each drainage pipe to the surface drainage system, and perform sealing and functional debugging. S6. Cyclic loading consolidation: Preload is applied to the foundation surface in stages, and after each load is applied or during the load maintenance, the gas pressurization equipment is activated, and the groundwater collected in the drainage well is actively discharged through the air lift drainage device, forming a cyclic operation process of loading and drainage until the foundation consolidation degree reaches the design requirements.

[0007] Preferably, before step S1, site pretreatment is also included: cleaning and leveling the surface of the site to be treated, and then laying a subbase.

[0008] Preferably, in step S2, a water-sand mixture is sprayed using a high-pressure jet grouting process to form the horizontal drainage layer.

[0009] Preferably, in step S2, a blind pipe is laid by traction drilling to form the horizontal drainage layer.

[0010] Preferably, in step S3, the vertical drainage body is a plastic drainage board, with a spacing of 1.0-1.5m, and its installation depth penetrates the entire soft soil layer to be treated.

[0011] Preferably, in step S4, the well pipe of the collection and drainage well is a steel perforated pipe with filter holes, the bottom of the steel perforated pipe is sealed, and the air inlet pipe and the drain pipe extend from the opening of the steel perforated pipe to a position 450-500mm away from the bottom of the pipe.

[0012] Preferably, the outer side of the steel pipe is wrapped with a reverse filter geotextile.

[0013] Preferably, in step S4, the bottom end of the air inlet pipe is bent to form a U-shaped pipe and inserted into the opening of the drain pipe.

[0014] Preferably, in step S6, the foundation surface is loaded by layering soil, laying water bags, or using dynamic compaction.

[0015] The present invention achieves the following technical effects compared to the prior art: This invention provides a rapid drainage and consolidation method for deep soft soil foundations. Through an innovative design of a three-dimensional interconnected structure of multiple horizontal drainage layers and vertical drainage bodies, the seepage path of water in soft soil is significantly shortened. This transforms the traditional bottom-up, vertical seepage drainage method in preloaded foundations into a multi-layered, vertically oriented seepage drainage system. This allows pore water at different depths to quickly converge into the vertical drainage body through the nearest horizontal drainage layer, significantly improving drainage efficiency. Furthermore, the overall seepage path of water in the preloaded foundation is changed from bottom-up against gravity to top-down in accordance with gravity, fully utilizing the soil's own weight consolidation and drainage effect. Under the same additional stress conditions, better treatment results can be achieved, and the problem of poor deep foundation treatment due to rapid attenuation of additional stress is solved. Simultaneously, a collection and drainage well is installed at depth, equipped with an air-lift drainage device. The pressure difference created by gas pressurization actively extracts groundwater, breaking through the depth limitations of conventional vacuum drainage methods using atmospheric pressure. Combined with staged loading and drainage cycle operations, the synergistic advancement of load application and water removal is achieved, effectively accelerating the consolidation process of the foundation soil. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Fig. 1 A flowchart of the rapid drainage and consolidation method for deep soft soil foundations provided by the present invention; Fig. 2 A cross-sectional schematic diagram of the drainage consolidation structure in the rapid drainage consolidation method for deep soft soil foundations provided by the present invention. In the diagram: 1. Gas booster pump; 2. Air inlet pipe; 3. Drainage pipe; 4. Steel perforated pipe; 5. Deep drainage well; 6. Plastic drainage board; 7. Horizontal drainage layer; 8. Preload. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] The purpose of this invention is to provide a rapid drainage and consolidation method for deep soft soil foundations to solve the problems existing in the prior art. The method has a simple structure, effectively reduces the construction period, effectively improves drainage efficiency, and effectively increases the treatment depth.

[0020] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0021] This invention provides a rapid drainage and consolidation method for deep soft soil foundations, such as... Figs. 1-2 As shown, it includes the following steps: S1. Drainage System Design: Based on geological survey data and construction period requirements, determine the number of horizontal drainage layers 7 to be set and their spacing. Based on geological conditions and construction period, rationally plan the key parameters of the horizontal drainage layer 7 to provide accurate guidance for subsequent construction, ensure that the drainage consolidation scheme can be optimized according to the actual site conditions, so as to meet the project's requirements for time and effect, and avoid construction delays or poor treatment effects caused by blind construction.

[0022] S2. Construction of horizontal drainage system: Multiple parallel horizontal drainage layers 7 are constructed from bottom to top at a predetermined depth in the soft soil foundation. By constructing multiple parallel horizontal drainage layers 7 from bottom to top, the traditional single vertical drainage path is changed, and vertical drainage is transformed into vertical multi-area layered drainage, which effectively shortens the drainage path, reduces drainage resistance, speeds up drainage, and thus improves the foundation drainage consolidation efficiency.

[0023] S3. Construction of vertical drainage system: Vertical drainage bodies are installed at the designed intervals within the site. The vertical drainage bodies intersect and connect with the horizontal drainage layers 7 of each layer, forming a three-dimensional underground drainage network. This allows water from different locations within the foundation to flow more smoothly into the drainage system, further improving the drainage path, comprehensively enhancing drainage efficiency, and strengthening the overall drainage and consolidation effect of the foundation.

[0024] S4. Construction of Deep Drainage Well 5: Drainage wells are constructed deep into the soft soil foundation within the site. An air-lift drainage device is installed inside the drainage well. The air-lift drainage device includes an air inlet pipe 2 and a drainage pipe 3 that are interconnected at the bottom. The drainage wells, being deep into the soft soil foundation, can collect deep groundwater. In conjunction with the air-lift drainage device, active drainage from the bottom can be achieved, breaking the limitations of traditional passive drainage from the top, effectively increasing the drainage depth, avoiding the rapid decay of treatment effect with depth, and improving the treatment capacity for deep soft soil foundations.

[0025] S5. Pipeline System Integration: Connect the air inlet pipes 2 of each collection and drainage well to the gas pressurization equipment, connect each drainage pipe 3 to the surface drainage system, and perform sealing and functional testing. Connect the gas booster pump 1 to provide power for air-lift drainage, ensuring effective drainage from the deep collection and drainage wells 5. Connecting the drainage pipes 3 to the surface drainage system provides a reasonable destination for the underground water. Sealing and functional testing ensures the stable and reliable operation of the entire drainage pipe system 3, preventing air or water leaks that could affect drainage performance.

[0026] S6. Cyclic Loading Consolidation: Preload 8 is applied to the foundation surface in stages. After each load is applied or during the load maintenance period, the gas pressurization equipment is activated to actively discharge the groundwater collected in the drainage well through the air lift drainage device, forming a cyclic operation process of loading and drainage until the degree of consolidation of the foundation reaches the design requirements. The application of preload 8 in stages, combined with the loading and drainage cyclic operation, can increase the pore water pressure of the soil while timely draining the water, accelerating the soil consolidation process, improving the foundation consolidation efficiency, ensuring that the foundation finally reaches the degree of consolidation required by the design, and guaranteeing the stability and bearing capacity of the foundation.

[0027] In a preferred embodiment, before step S1, site pretreatment is included, which involves cleaning and leveling the surface of the site to be treated, followed by laying a subbase. The subbase is a compacted graded sand and gravel subbase with a thickness of 30-50cm. Cleaning and leveling the site removes debris, creating favorable conditions for subsequent construction and preventing site debris from affecting the operation of construction equipment and the construction quality of the drainage system. Laying the compacted graded sand and gravel subbase forms a hard shell layer, improving the bearing capacity of the soft soil foundation surface, facilitating the entry and operation of construction machinery, and preventing excessive disturbance of the soft soil foundation by construction machinery.

[0028] In a preferred embodiment, in step S2, a water-sand mixture is sprayed using a high-pressure jet grouting process to form a horizontal drainage layer 7. The resulting horizontal sand layer has a thickness of 20-30 cm, and the jet grouting point spacing is 50-80 cm. The high-pressure jet grouting process ensures the uniform distribution of the water-sand mixture, forming a continuous horizontal sand layer of suitable thickness. Reasonable control of the sand layer thickness and jet grouting point spacing helps ensure the drainage performance of the horizontal drainage layer 7, ensuring that it provides a good drainage channel while possessing a certain degree of stability and load-bearing capacity, thus improving the effectiveness and durability of the horizontal drainage layer 7.

[0029] In a preferred embodiment, in step S2, blind pipes are laid using a horizontally directional drill to form a horizontal drainage layer 7. The blind pipes are perforated HDPE double-wall corrugated pipes with a diameter of 100-150mm, and the elevation deviation of the blind pipes in the same layer is controlled within ±5cm. Using a horizontally directional drill for laying the blind pipes ensures high construction precision and effectively controls the laying position. HDPE double-wall corrugated pipes have good flexibility, corrosion resistance, and drainage performance, and the perforated design facilitates groundwater inflow. Controlling the elevation deviation of the blind pipes in the same layer ensures smooth drainage of the horizontal drainage layer 7 and avoids localized water accumulation due to excessive elevation deviation, which would affect the drainage effect.

[0030] In a preferred embodiment, in step S3, the vertical drainage body is a plastic drainage board 6, installed at intervals of 1.0-1.5m, and its installation depth penetrates the entire soft soil layer to be treated. The plastic drainage board 6 has good drainage performance and a certain strength, effectively shortening the horizontal drainage path. The reasonable installation interval ensures drainage effectiveness while avoiding material waste and increased construction costs due to excessively small intervals. The installation depth penetrates the entire soft soil layer to ensure that all water within the soft soil layer can flow into the horizontal drainage layer 7 through the vertical drainage body, achieving comprehensive and efficient drainage and consolidation.

[0031] In a preferred embodiment, in step S4, the well pipe of the collection and drainage well is a perforated steel pipe 4 with a diameter of 300-500mm. The bottom of the perforated steel pipe 4 is sealed. The air inlet pipe 2 and the drain pipe 3 extend from the opening of the perforated steel pipe 4 to a position 450-500mm from the bottom of the pipe. The perforated steel pipe 4 ensures that groundwater can smoothly enter the well pipe while preventing soil from the surrounding well wall from entering and clogging the well pipe. A suitable pipe diameter can meet the drainage requirements of a large flow rate. Extending the air inlet pipe 2 and the drain pipe 3 to a specific position from the bottom of the pipe ensures the normal operation of the air-lift drainage device and prevents water from accumulating at the bottom of the pipe, thus ensuring that the collection and drainage well efficiently collects and discharges groundwater.

[0032] In a preferred embodiment, the outer side of the steel pipe 4 is wrapped with a reverse filter geotextile, the equivalent pore size of which is no greater than 0.075 mm and the permeability coefficient is no less than 1×10⁻⁶. -3 With a permeability of cm / s, the reverse filter geotextile can further prevent soil particles from entering the well pipe, ensuring the smooth flow of the collection and drainage well. At the same time, its high permeability coefficient ensures that groundwater can smoothly pass through the geotextile into the steel pipe 4, playing a good filtering and permeability role, and improving the working stability and reliability of the collection and drainage well.

[0033] In a preferred embodiment, in step S4, the bottom end of the air inlet pipe 2 is bent into a U-shape and inserted into the opening of the drain pipe 3 to a depth of 10-20 cm. The outer diameter of the air inlet pipe 2 is 20-30 mm, and the inner diameter of the drain pipe 3 is 50-80 mm. The U-shape of the air inlet pipe 2 effectively prevents gas from overflowing from the drain pipe 3 during drainage, ensuring effective air-lift drainage. The appropriate outer diameter of the air inlet pipe 2 and the inner diameter of the drain pipe 3 ensure sufficient gas flow to drive drainage and meet drainage requirements, guaranteeing efficient operation of the air-lift drainage device.

[0034] In a preferred embodiment, in step S6, the foundation surface is loaded by layering soil, laying water bags, or using dynamic compaction. The rate of application of the preload 8 is controlled so that the daily increment does not exceed 1 / 3 of the calculated ultimate bearing capacity of the foundation. The duration of a single continuous loading cycle is 3-5 days, and the duration of a single continuous drainage cycle is 1-2 days. Multiple loading methods can be flexibly selected according to the actual engineering conditions to meet different site and engineering requirements. Controlling the rate of the preload 8 can prevent foundation instability caused by excessive loading, ensuring the safety and stability of the foundation during the loading process. Reasonably setting the duration of a single continuous loading cycle and drainage allows sufficient time for the soil to drain and consolidate, improving the efficiency of the loading and drainage cycle and effectively promoting foundation consolidation.

[0035] Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. Furthermore, those skilled in the art will recognize that, based on the ideas of this invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A rapid drainage and consolidation method for deep soft soil foundations, characterized in that: Includes the following steps: S1. Drainage system design: Based on geological survey data and construction period requirements, determine the number of horizontal drainage layers and their spacing. S2. Construction of horizontal drainage system: Construct multiple parallel horizontal drainage layers at a predetermined depth in the soft soil foundation from bottom to top; S3. Construction of vertical drainage system: Vertical drainage bodies are installed on the site at the designed intervals. The vertical drainage bodies intersect and connect with the horizontal drainage layers of each layer. S4. Construction of deep drainage wells: Drainage wells are set up in the site to penetrate into the soft soil foundation, and an air-lift drainage device is installed in the drainage wells. The air-lift drainage device includes an air inlet pipe and a drainage pipe that are interconnected at the bottom. S5. Pipeline system integration: Connect the air inlet pipes of each of the above-mentioned collection and drainage wells to the gas pressurization equipment, connect each drainage pipe to the surface drainage system, and perform sealing and functional debugging. S6. Cyclic loading consolidation: Preload is applied to the foundation surface in stages, and after each load is applied or during the load maintenance, the gas pressurization equipment is activated, and the groundwater collected in the drainage well is actively discharged through the air lift drainage device, forming a cyclic operation process of loading and drainage until the foundation consolidation degree reaches the design requirements.

2. The rapid drainage and consolidation method for deep soft soil foundations according to claim 1, characterized in that: Before step S1, site pretreatment is also included: cleaning and leveling the surface of the site to be treated, and then laying the subbase.

3. The rapid drainage and consolidation method for deep soft soil foundations according to claim 1, characterized in that: In step S2, a water-sand mixture is sprayed using a high-pressure jet grouting process to form the horizontal drainage layer.

4. The rapid drainage and consolidation method for deep soft soil foundations according to claim 1, characterized in that: In step S2, blind pipes are laid by horizontal directional drilling to form the horizontal drainage layer.

5. The rapid drainage and consolidation method for deep soft soil foundations according to claim 1, characterized in that: In step S3, the vertical drainage body is a plastic drainage board, which is installed at a spacing of 1.0-1.5m and its installation depth penetrates the entire soft soil layer to be treated.

6. The rapid drainage and consolidation method for deep soft soil foundations according to claim 1, characterized in that: In step S4, the well pipe of the collection and drainage well is a steel perforated pipe with filter holes. The bottom of the steel perforated pipe is sealed. The air inlet pipe and the drain pipe extend from the opening of the steel perforated pipe to a position 450-500mm away from the bottom of the pipe.

7. The rapid drainage and consolidation method for deep soft soil foundations according to claim 6, characterized in that: The steel pipe is wrapped with a reverse filter geotextile.

8. The rapid drainage and consolidation method for deep soft soil foundations according to claim 1, characterized in that: In step S4, the bottom end of the air intake pipe is bent to form a U-shaped pipe and inserted into the opening of the drain pipe.

9. The rapid drainage and consolidation method for deep soft soil foundations according to claim 1, characterized in that: In step S6, the foundation surface is loaded by layering soil, laying water bags, or using dynamic compaction.

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